Low birthweight (LBW) may put children at risk for behavior problems due to the increased likelihood of perinatal brain injury. In addition to Cerebral Palsy and mental retardation, perinatal brain injury may be associated in childhood with mild motor impairment and learning disabilities, which are known to increase children's risk for behavior problems. The availability of cranial ultrasound techniques, combined with increased survival in LBW, renders important the investigation of potential links between LBW, brain injury, and behavioral outcome. We propose an epidemiological study of behavior problems at 66 months in a longitudinal cohort of children that is unique in at least three respects: 1) All were screened in the neonatal period with serial cranial ultrasound for evidence of central nervous system (CNS) injury; 2) the cohort represents 90% of all infants who weighed 2000 g or less at birth in a geographically defined region in 1984-1987; and 3) intermediate data on major neurologic handicap at 24 months are available on the entire cohort, and intermediate data on infant temperament, maternal distress, and the home environment at 12 and 30 months of age are available on a regional subgroup of the cohort. The specific aims of the project are to determine the nature of the relationship between perinatal brain injury and subsequent behavior problems, and to determine the role of potential confounders, mediators, and moderators of this relationship, such as other birth characteristics, motor, cognitive, and language development, infant temperament, and the child's environment (maternal distress, marital dysfunction, family structure, and child-oriented qualities of the home). Assessments will take place in the home at age 66 months, and both mother (or primary caregiver) and child will be interviewed; information on the child's behavior will be obtained from at least one other informant. The evaluation will include child behavior problems, adaptive behaviors, cognition, language, and aspects of the child's environment. Both cross sectional and longitudinal analyses are planned to investigate the role of brain injury (and type of brain injury) alone and in combination with other child and environmental variables in determining behavioral outcome. The age chosen for study represents an opportunity to assess behavior problems prior to school entry to avoid the possible confounding effects of school failure, as well as to identify potential indicators of later behavior problems. The overall goals of the project are to determine the prevalence of preschool behavior problems in a large cohort of LBW children from the era of newborn intensive care and to determine the nature of the relationship between perinatal brain injury and behavior problems in these children.